January 31, 2012

I had to address an issue last week on a client's bike that had to do with the front derailleur mount on his 2011 Felt F1. I did the frame-up build with Shimano Dura Ace Di2 in the early part of this past summer. This bike was not abused and I'd have to give a gold star to this client because of how well he takes care of his bikes. So, here's a short description of the issue and then my fix...

After inspection, it was obvious that the front derailler mount seperated from the frame. Two of the three rivets used to attach the mount to the carbon seattube were floating in the hole that they were innitially installed in and both of the holes were now larger in diameter than they originally were because of the damage caused by the rivets installed at the factory.

The first two photos are with the Di2 front derailleur and without.

I initially thought that the failure was mainly caused by the different and greater forces introduced by the Di2 front derailleur in addition to possibly a poorly installed blind rivet (see third photo).

After retreveing from inside the frame and inspecting the other two rivets I came to another conclusion.... I believe that this failure was because of the type of blind rivets used. Based on my inspection and research, the blind rivets that Felt used were either completely the wrong spec based on the materials being joined (composite and aluminum) or they didn't account for the stronger force that is applied to the area by the Di2 front derailleur. From what I can tell, the rivets that Felt used are sometimes called multigrip rivets because they can be used in applications where the hole is irregular or oversized. This type of blind rivet body expands to fill the hole. All three rivets did not expand against the internal surface of the carbon seattube. Because of this, one of the three rivets seperated completely from the frame while one of the others was loose.

So here's what I did to repair and make it better that it was when it came out of the factory....

I special ordered a blind rivet that with the dimensions that would work with the existing components and the combined material thicknesses. This type of rivet is sometimes referred to as a press plate rivet.

I wanted to test the press plate rivet and compair it to the OE rivet. I did this with a section of carbon steer tube (see photo). The one on the left is the OE rivet and the one on the right is the upgraded replacement.

I was satisfied that this was a good solution. Besides the different rivets, I wanted to bond the mount to the seattube with epoxy just for good measure.

The repair was pretty straight forward. I started by applying some epoxy in and around the two damaged holes in the frame. After in cured, I redrilled/cleaned the two holes to the correct diameter. I then burnished the inside surface of the front derailleur mount in order to improve adhesion. I then applied epoxy to the frame, installed the three rivets, insured alignment and fit and then I let it cure.

As you can see the the last image, the rivet heads are obviously a larger diameter and not as pretty as the original rivet heads. In this situation, I choose structural integrity over cosmetic appeal. The end result was better than when it was new.

In closing, I believe that we are going to see more of this problem moving forward with more and more Di2 front derailleurs and the like being used, specifically on carbon frames that do not use a front derailleur clamp. Let me know what you think. Thanks for checking in. -John

September 14, 2009

Way back in September of 2008, I published my initial post about what I thought was a problem with the Ultra-Torque design. Now going on a year later, I am even more confident with my initial theory. But now I have a solid solution to the problem that some who have a Campagnolo Ultra-Torque crankset/bottom bracket may have experienced.

First, I want to make a couple points...

I will not deny that for the most part, Ultra-Torque is a good design. Where it fails is in its capability to allow for shell width variances. This may seem like a a minor flaw, but it has major consequences.

For the life of me, in this day and age, and with all of the current technology, why can't frame manufactures make their 68mm bottom bracket shells 68mm and their 70mm shells 70mm?!?! If this was the case, there wouldn't be a need for the wavy washer in the Ultra-Torque design.

The wavy washer is a legit component in certain applications in many industries. But in this instance, it's a band-aid.

If it's OK to have axial or lateral movement to the non-drive side, why is the Ultra-Torque design the ONLY design out there that has this movement? If any of the other systems exhibit this movement, it means that either the bearings are shot, or you didn't install the proper bottom bracket and/or spacers.

Based of the volume of emails and comments I have been receiving about this "non-issue", I believe that it's fairly common. Over the last few months, I have applied my "fix" to several bikes. All with success. The end result has been a very smooth, very stiff, axial-movement free Ultra-Torque system. Just now I believe Campagnolo wanted to be. Next up, step by step details. Thanks for checking in. -John

Client Testimonials...

A.R. said...

" Dear John,
I got out tonight for a quick ride... The Trek ran like a top, like butter on a hot skillet, smooth like a baby's bottom, like a shot of Johnnie Walker Blue, . . well you know what I'm trying to say, like a brand spanking new 5.9 Madone! Thank you again for another job well done!
Your grateful customer and greatest billboard,
A.R"

PR said...

"My search for a highly qualified, honest and reliable bike mechanic is over. Not only is John (RogueMechanic) a superb mechanic, he is also very knowledeable about equiptment... I have never been disappointed."

Dr. M said...

"John is a top flight mechanic. His knowledge, expertise and superb customer service surpasses everyone else... His personal integrity and high standards are reflected in his work on my bikes..."